Replace the convoluted useAccountSession composable with a pinia store
that in addition allows for the consolidation of all session related
functions to grouped into one module.
Provide a basic account system with login and server side session store
identified by a cookie. Upon successful login a signed session cookie
is set by the server with the session stored on the server identifying
which account it is logged in as. The client uses a shared useFetch on
the session endpoint to identify if it's logged in and which account it
is logged in as, and refreshes this when loggin in or out.
